This module is under development! Use at your own risk.
SunPy currently supports reading dynamic spectra from e-Callisto instruments.
The main class that is used for this is
CallistoSpectrogram. SunPy also
comes with an example image that shows a radio burst observed at Rosse Observatory (aka. BIR; Birr Castle, Co. Offaly, Ireland) that
can be found in sunpy.data.sample.CALLISTO_IMAGE.
import matplotlib.pyplot as plt import sunpy.spectra import sunpy.data.sample from sunpy.spectra.sources.callisto import CallistoSpectrogram image = CallistoSpectrogram.read(sunpy.data.sample.CALLISTO_IMAGE) image.peek()
We now notice that there seems to be something interesting that has been cut off at the corner of the image, so we use the extend method to request more data from the server. It optionally takes the amount of minutes we want to request from the server (negative values mean we want to add data that was registered before our existing local data), if none are given it defaults to 15 minutes (the size of one e-Callisto file).
more = image.extend() more.peek()
We will, for the purposes of this demonstration, continue working with the original image, though.
You can then perform automatic constant background subtraction by using the
method. The resulting image will be clipped at 0 using the
min parameter of
peek in order to avoid negative values.
from matplotlib import pyplot as plt import sunpy import sunpy.data.sample from sunpy.spectra.sources.callisto import CallistoSpectrogram image = CallistoSpectrogram.read(sunpy.data.sample.CALLISTO_IMAGE) nobg = image.subtract_bg() nobg.peek(vmin=0)
If you want to see the background determined by the automatic subtraction,
you can use the
method and visualize the resulting
plt.figure() bg = image.auto_const_bg() plt.plot(image.freq_axis, bg) plt.xlabel("Frequency [MHz]") plt.ylabel("Intensity") plt.show()
Now let us say we want to isolate the interesting bit (which starts around
10:38) from the boring background; there is a method called
that allows us to take the part of an image that is
within a specified interval. Leaving out the second argument it defaults
to the end time of the file.
import matplotlib.pyplot as plt import sunpy import sunpy.data.sample from sunpy.spectra.sources.callisto import CallistoSpectrogram image = CallistoSpectrogram.read(sunpy.data.sample.CALLISTO_IMAGE) nobg = image.subtract_bg() interesting = nobg.in_interval("10:38") interesting.peek(vmin=0)
To get rid of the noise, we could also clip low intensities by setting vmin.
If we want more context, we can also join together different images into a large one in time (note that this does more than just concatenating the array and the axes – it also considers possible overlap or gaps).:
c1 = CallistoSpectrogram.read('BIR_20110922_101500_01.fit') c2 = CallistoSpectrogram.read('BIR_20110922_103000_01.fit') d = CallistoSpectrogram.join_many([c1, c2])
We could also get the from_range method to get data between those two points directly from the archive and joined together (though that will fetch all frequencies of BIR):
from sunpy.spectra.sources.callisto import CallistoSpectrogram d = CallistoSpectrogram.from_range('BIR', '2011-09-22 10:15:00', '2011-09-22 10:45:00')